Various types of blades are known. In current practice the known types are generally characterized by a continuous surface of a certain width, which support the wire transversely and across its direction of forward movement. Said surface must be maintained in a space in a pre-set position and with a very careful geometrical precision; this is obtained by providing a suitable beam, which serves to support said continous surface.
So as to make possible a practical use of the blades, in current known techniques a composite blade is utlized in which there are a carrier part and a sliding part, the two parts being joined or held together by means of screws, dovetailing or other mechanical means.
With the technology used so far, blades formed of one single block have been neither practical in use nor convenient.
Known types of blades essentially have the following defects; they are expensive and heavy; they require multiple and complex processing and they are not easy to handle.